1. Field of the Invention
The subjection relates generally to material moving apparatus and more particularly to improvements in belt trippers or hoppers which ride on a conveyor assembly.
2. Description of Related Art
A conventional belt tripper 11 is illustrated in FIG. 1. Such a belt tripper 11 typically travels up and down railroad tracks located on top of a long movable conveyor 13 as shown in FIG. 2. The tripper 11 functions to "trip" material off the long conveyor 13 to a short conveyor 15, which builds a stack of material 14. Apparatus known as "hoppers" are also similarly arranged to move up and down conveyors such as conveyor 13 to carry material along the conveyor. Trippers and hoppers of conventional design have exhibited numerous drawbacks.
First, conventional trippers/hoppers 11 ride on rail wheels 17, as shown in FIG. 3. Typical rail wheels 17 have a flange 18 running on the inside of the rail 19. These flanges 18 help guide and align the wheel 17 along the track, but are subject to derailment if the track is not even. This poses a serious safety concern: since it permits the tripper/hopper to derail, i.e., come off the top of the bridge 13.
Current equipment designs further use a pad type brake 21, FIG. 4, that applies pressure to the top of the rail 19, using the weight of the tripper/hopper car. This design is similar to the braking system used on old trolley cars. The amount of friction developed is proportional to the weight of the machine and the spring tension.
Current equipment designs use dual wire ropes running the length of the bridge 13 that wrap around capstans on the tipper/hopper. Propulsion of the tripper/hopper is achieved by powering the capstans. Several problems exist with this system. With wire rope (cables), stretch is experienced as tension is applied through the capstans. The tripper/hopper's mass, plus the differential forces produced by the belt tensions, have to be overcome or resisted by the wire ropes. Overcoming the wire rope's stretch produces a jerky propulsion movement.
In addition, since the tensions on the wire rope can become different from side to side, the resulting forces can create racking and potentially can derail the tripper/hopper. The same difficulty could be experienced if one of the cables breaks. As stated above, only the flanges of the rail wheels keep the current design on the rails, and if it derails, the brakes are useless.